System and method for PC-based video conferencing and audio/video presentation

ABSTRACT

A video conferencing/presentation system includes a PC docking station and a room media unit. The dock includes speakerphone and tactile user interface. The wall-mounted RMU, including a wide field camera and speaker(s), is coupled to a monitor. The dock communicates with the RMU. A speakerphone mic captures room audio. During conferencing, room audio and camera video are sent to a docked PC; the PC communicates with remote nodes using video chat software, sending room A/V; remote A/V is received from the PC by the dock, and transmitted for RMU output. During presentation, room audio, and/or PC media software presentation, may be output through the RMU, or to the PC for remote transmission. The dock provides the PC network access. Dock/RMU may each be equipped with a bidirectional transceiver, which uses prioritized opportunistic sequencing to assemble/disassemble a combined media/control packet stream over a cable, and transfer power from dock to RMU.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/833,555, filed Jun. 11, 2013, and entitled “System and Method forPC-Based Video Conferencing and Audio/Video Presentation”, which ishereby incorporated by reference. This application is a continuation ofU.S. application Ser. No. 13/960,066, filed Aug. 6, 2013, and entitled“System and Method for PC-Based Video Conferencing and Audio/VideoPresentation”, which is hereby incorporated by reference. Thisapplication is related to U.S. Utility application Ser. No. 13/960,113,filed Aug. 6, 2013 and entitled “Bidirectional Transceivers UsingOpportunistic Sequencing”, which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to video chat/conferencing andpresentation audio/video systems. More particularly, the presentinvention relates to a system and a method for extending PC videochat/conferencing functionality, and presentation audio/videofunctionality, to a conference room setting.

BACKGROUND OF THE INVENTION

Software that facilitates real time audio and video conversation betweentwo individuals over a communication system is well-known. Thecommunication system may be, for example, the Internet, a local areanetwork, a telephone network, or some combination of communicationsystems. Typically, each individual executes a respective copy of thesame video chat software program on a personal computer or other smartdevice, such as a cell phone, a tablet computer, a portable mediaplayer, or an e-reader. We will refer to such devices, which include aprocessor and an operating system, collectively as “computers” or “PCs”.

Individuals participating in a video chat session may use the same typeof PC, or different types, so long as each PC implements a version ofchat software that is compatible with the others. A video stream may becaptured by a webcam built into, or coupled with, the PC; an audiostream, by a microphone, either external from, or internal to, the PC.The other participant(s) receive that video and typically display it ona screen that is built into their PC. They listen to the audio using oneor more PC speakers, external speakers, or a headset. Text messagingcapability and other capabilities, such as file transfer and clickablehyperlinks, are often facilitated by the software. Examples of suchsoftware, which we will refer to as “video chat software”, includeSkype®, Yahoo!® Messenger, and Google Voice™. Such video chat softwareis available to the public for immediate download from the Internet, atlittle or no cost.

Some modern video chat software is not limited to two participating PCs.When the software enables three or more participants, each participantmay be able to see each of the other participants simultaneously inseparate windows on a split screen, or may be able to toggle amongwindows displaying the individual participants.

We will use the term “real-time” in connection with audio and videostream transmission by video chat software. Although no transmission isactually instantaneous, by “real-time” or “instantaneous” we meanwithout systematic delay significant enough as to be noticeable by mostpeople.

SUMMARY OF THE INVENTION

Inexpensive or free video chat software directed toward individualparticipants is widely used. Two or more people can agree on a videochat software package, and if they do not already have the softwareinstalled on their PC, they can typically download it from the Internet,install it, and be video and audio chatting within minutes.

PC webcams, microphones, speakers, and displays are typically designedfor use by a single individual who is operating the PC at the time. Butin business contexts, a common scenario is a meeting in a conferenceroom, with one or more individuals, who cannot be physically present,participating by conference phone. Two remotely-located companies, eachwith its own conference room containing several individuals, may engagein some negotiation over a chat facility. A family may gather in a roomto chat with one or more relatives based overseas. A student might needto participate in a class meeting while off campus.

Consider, as a particular example, the human resources (HR) departmentof a company, which routinely interviews applicants, from a national orglobal pool, for job openings. The company wants to conduct preliminaryinterviews of remote applicants in order to select a short list who willbe flown to company headquarters for more in-depth interviews. On amoment's notice, the company would like to gather stake-holders in thehiring decision (e.g., the prospective boss, internal clients,co-workers, and an HR representative) in a conference room, and meeteach of the remote candidates face-to-face.

From the perspective of a candidate, for this to be feasible over theInternet, the candidate must have access to hardware and software thatfacilitates video conferencing. For this to be affordable, access tothese resources must be free, or at no cost to the candidate or to thecompany. For this to be timely, access by the candidate to theseresources must be effectively immediate. For this to be workable fromthe perspective of the interviewers, the group node must have audio andvideo capabilities that are adequate for several people gathered in theconference room and speaking from their individual seats without passinga microphone around.

A solution is to use a PC executing ubiquitous video chat software suchas Skype®, but, in the group node, effectively replace the microphone,camera, speaker, and/or display devices of the PC with equipment that isadequate for a conference room environment. Virtually every candidatewill already own, or have access to, a PC that can run video chatsoftware. If they do not have compatible software already installed,they may be able to download and install it for free, in minutes.

The company does not need to pay for expensive video conferencingsoftware or special communication equipment. They can simply use anexisting PC, supplemented with a system to couple that PC withperipheral devices more appropriate for a group environment. Aconference room could be equipped for video conferencing almostinstantly, using an existing PC running chat software, using concepts ofthe invention. In the negotiation scenario mentioned above, the twocompany teams can each participate using the same approach. Video chatsoftware may facilitate two or more nodes. Using the concept of theinvention, each node can be an individual node or a group node.

Such advantages may be achieved with a system that includes a PC dockingstation (dock) and a room media unit (RMU), coupled to each other by acommunication system. The dock includes interfaces for connecting orcommunicating with a PC, whereby audio, video, and/or control streams,and/or network access may be exchanged between the PC and the dock. Thedock may include a microphone, which might be part of a speakerphone.The speakerphone may include an interface for connection to a telephonecommunication system. The dock may include a bridge that provides the PCwith pass-through access to the telephone system. The microphone (mic)is used to capture sound from the room, such as speakers' voices, totransmit to remote individual and group “nodes” via the video chatsoftware. The mic may employ echo cancellation technology. The dock mayinclude a tactile user interface for control of the system; the dock mayinclude a display, which might be a touch display.

In many cases, organizations (e.g., companies and educationalinstitutions) allow their PCs to connect to the Internet only throughthe organization's internal local network. Thus, the dock may provide aninterface for pass-through of a network connection, such as the Internetor a local area network, to a connected PC.

The RMU includes a housing, and may or may not include one or moremounting mechanisms, such as brackets, hooks, wires, eye hooks, ormounting plates, adapted to attaching the housing to a wall; if so, theRMU may be referred to as a “wall unit.” The RMU might alternatively beused without wall mounting; for example, resting on a bookcase or afiling cabinet.

The RMU may include, or be coupled to, a video camera to capture localvideo to be transmitted to the remote nodes. Preferably, the camera willat least have the capability to cover a wide field-of-vision angle(e.g., at least 70 degrees, or at least 80 degrees) sufficient to coverrelevant portions of a room, such as the people at a conference table.One or more video cameras may be incorporated into the RMU housing; oneor more video cameras may be external to the RMU housing, but controlledat least in part by logic in the RMU. If more than one camera are partof the system, they may complement each other in functionality, and eachmay be chosen to operate with any desired degree of “intelligence”.

The RMU may contain, or be coupled with, one or more speakers,preferably ones of significantly better quality than those that todaycommonly come installed in laptop computers. When the system is used ina conference mode, the speakers output to the room sound received fromthe remote nodes. When the system is used in a presentation mode, thespeakers may output the voice of a presenter.

The RMU may have an interface to communicate with one or more monitorsor televisions, or it might include a monitor(s) or television(s)internally. A “monitor” might be a screen onto which a video stream isprojected. When the system is used in a video conferencing mode, themonitor/TV outputs to the room video received by the PC from the videochat software. When the system is used in a presentation mode, themonitor may show the speaker's image and/or presentation content, suchas a video or a slideshow.

Communication between the dock and the RMU may use any system, wired orwireless—any audio/visual (A/V) “pipe” capable of transmitting andreceiving audio, video, and control information as required for thecombined functionality of the dock and the RMU. Preferably, suchcommunication will be based on a single cable, such as an inexpensive,off-the-shelf cable such as CAT 5, CAT 6, or CAT 7 cable. The dock andRMU may reformat the audio, video, and control information fortransmission through the dock-RMU communication system, or “audio/visual(A/V) pipe”. The dock and RMU may packetize information to be sentthrough the pipe. They may prioritize information (e.g. by type—audio,video, or control) to be sent through the pipe. They may interspersepackets of different types, and use information stored within thepackets (e.g., a packet header) to synchronize and restore the originalaudio and video streams (or something very close to the originalstreams) in real time (see definition above). They may exchange audioand video information in uncompressed form.

A pair of transceivers might be used to perform the packetizing andscheduling functions of the dock and RMU. A configuration for a pair ofbidirectional transceivers is described below. As will be clear fromthat description, these transceivers have much wider applicability thandock-RMU communication.

Embodiments of the bidirectional transceivers might be incorporated intoany pair of media appliances; the dock and RMU are illustrativeappliances. The transceivers may transmit and receive audio, video,control streams, and/or network information over a cable, such as CAT 5,CAT 6, or CAT 7, in either or both directions. Other cable types mayalso be used for the A/V pipe; preferably, they will have transmissionspeeds in both directions at least as fast as CAT 5, and have anarchitecture that incorporates at least four differential pairs ofwires. Compromises may be made in audio resolution, video resolution,and/or frame rate to accommodate slower cable architectures. CAT 6 canhandle 60 frames/s video, combined with audio and control streams. Sincecinema is generally presented at only 24 frames/s, some compromise ofthe 60 frame rate can be made without noticeable degradation in videoquality. Two differential pairs may carry media content in bothdirections, and two differential wire pairs may carry network access inboth directions. The media content may include packetized and combinedaudio and video streams; the media content may also include control datafor exchanging control or status information between the mediaappliances. The two network pairs may also be used to carry electricalpower from one of the appliances to the other.

To carry media (audio and video, and possibly control) streams from asource device (e.g. a PC) to a destination device (e.g., a speaker or amonitor), one transceiver will act as transmitter; the other, receiver.The transmitter may include reformatter logic (i.e., hardware, orsoftware instructions that are accessed from tangible media and executedby a processor or processing system), that reformats media informationfor transmission through the pipe; packetizer logic that create packetswhich incorporate data (e.g., packet headers), thereby allowing thepackets to be later converted back into streams; adaptive ratemultiplexer logic, which sequences and assembles the packets into anintegrated media stream; and a transport layer, to provide physicalinterfaces of transmitter elements to a CAT 6 or other cable interface.

The receiving transceiver may include a transport layer, to couple CAT 6or other cable interface to physical interfaces of receiver elements;adaptive rate demultiplexer logic, which disassembles the integratedmedia stream into packets, and then resequences the packets forreconstruction into the separate audio, video, and control streams;depacketizer logic, that removes headers from the packets and extractsthe audio, video, and control information from the packets; reclockerlogic to reconstruct the timing and synchronization of the audio andvideo streams; and reformatter logic to convert the stream formats ifnecessary for transmission to the destination.

A given transceiver may combine some or all of the transmitting andreceiving functionality. Preferably the transceiver will be fullybidirectional, implementing all functionality for both simultaneouslytransmitting and receiving. Some elements executing particular logicfunctions may be hardware components; some logic functions may bedispersed over two or more hardware components; and one hardwarecomponent may perform two or more logic functions. Henceforth, when werefer to a component such as a “multiplexer”, the reader shouldunderstand that to mean multiplexer logic, which might or might notcorrespond to a single hardware component.

The adaptive rate multiplexer may prioritize which type of informationgets inserted next into the media stream. For example, in order ofdecreasing priority: audio, control, and video; in other words, videopackets will only be inserted when there are no audio or control packetsto insert. Audio preferably has the highest priority because errors oroffsets in audio are typically most noticeable to humans. Otherprioritization schemes are, of course, possible. We call suchprioritization of bandwidth “opportunistic sequencing” of packets whenbuilding the integrated media stream.

Opportunistic sequencing might not perfectly reproduce video and audiostreams if the video stream were artificially generated from randomlygenerated data (making, in general, each pixel have a different colorfrom its neighbors), because the entire bandwidth of the media streamcould be exhausted or exceeded by the assembled combination ofinformation types. This limitation is theoretical, however, and inhandling real-world video chat sessions, it would be rare if thetransmitter failed to find room for all types of packets. Although theinformation can be transmitted uncompressed (and hence, there is no dataloss due to compression), the reconstructed streams may not be perfectlytrue to the original audio and video streams, since the reclockers mayperform interpolation of opportunistically-sequenced packets, in orderto obtain the correct clock rate and synchronize the audio and videostreams. A few packets may be dropped or ignored, but in real-worldcontexts, these losses are trivial compared to loss introduced by lag inrunning the video chat software, arising from network latency, slow PChardware, and marginal PC graphics resolution.

The transceivers may use buffers to hold data being processed. Thetransceivers may include a protocol channel, whereby one transceiver cansignal the other transceiver that a buffer is full or nearly full. Atransceiver receiving such a signal may respond by slowing down, orstopping processing; upon receiving an “all clear” signal, normalprocessing can resume.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a conceptual diagram illustrating a video chat session, or apresentation session, between a local group node and an individual node.

FIG. 1b is a conceptual diagram illustrating a video chat session, or apresentation session, among a local group node and two individual nodes.

FIG. 1c is a conceptual diagram illustrating a video chat session, or apresentation session, between a local group node and a remote groupnode.

FIG. 1d is a conceptual diagram illustrating a video chat session, or apresentation session, among two group nodes and an individual node.

FIG. 2a is a block diagram illustrating components of a PC serving as alocal node, and some of the types of devices that might play the role ofthe PC.

FIG. 2b is a block diagram illustrating components of a group node in aPC-based video conferencing system.

FIG. 3 is a conceptual diagram illustrating components of a PC-basedvideo conferencing system, serving as a local group node in a videochat, or a media presentation, session with two remote nodes.

FIG. 4 is a schematic diagram illustrating a dock, including logiccomponents and interfaces, of a PC-based video conferencing system.

FIG. 5 is a schematic diagram illustrating a room media unit (RMU),including logic components and interfaces, of a PC-based videoconferencing system.

FIG. 6 is an information flow diagram illustrating the flow of real-timeaudio and video streams from a remote node to a PC-based videoconferencing system.

FIG. 7 is an information flow diagram illustrating the flow of real-timeaudio and video streams to a remote node from a PC-based videoconferencing system.

FIG. 8 is a conceptual diagram showing bidirectional transfers ofvarious types of information (e.g., audio, video, network, and control)between a pair of transceivers.

FIG. 9 is a block diagram that illustrates the transport layer of a pairof bidirectional transceivers.

FIG. 10 is a block diagram that illustrates the data and protocol layersof a media transmitter-receiver pair.

FIG. 11 is a block diagram that illustrates interpolation of audioframes by an audio interpolation reclocker.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Introduction

This description provides embodiments of the invention intended asexemplary applications. The reader of ordinary skill in the art willrealize that the invention has broader scope than the particularexamples described in the text and accompanying figures. For example, wewill use a conference room in our discussion for illustrative purposes.The system might be used in other contexts, such as a home, or evenoutdoors.

A few notes are in order about conventions that are followed in thedescription and claims. The third, or third and fourth, digits from theright of a reference number indicate the first figure, or group offigures (e.g., FIG. 1a-1d ), in which the item to which the referencenumber occurs first appears. A single item may be tagged with more thanone reference number to indicate an “is a” relationship. For example, anitem may be both a node and a group node. A group node is a node. Allnodes, whether individual or group, share some characteristics; groupnodes have some specific characteristics not shared by individual nodes,and conversely.

The conjunction “or” is used inclusively (e.g., A or B is true if A istrue, if B is true, or if both A and B are true), unless otherwise clearfrom the context. “Logic” includes logic in hardware; and/or logic insoftware instructions, accessed from tangible storage and executed by aprocessor or processing system.

Room Video Chat System

Overview

FIG. 1a-1d illustrate some of the possible video chat configurationsinvolving a group node 110. In each case, the video chat among nodes 100occurs over some communication system 160. For our purposes, acommunication system 160 is any system of hardware and software thatfacilitates the transmission of audio and visual information inreal-time (defined previously), such as the Internet or a local areanetwork. We use the term recursively so any communicatively-coupledcombination of communication systems 160 is itself a communicationsystem 160. The communication may be two-way, as indicated by arrows,typified by 161.

The cases shown illustrate a video chat session between or among nodes100, specifically: a group node 110 and an individual node 120 (FIG. 1a); a group node 110 and two individual nodes 120 (FIG. 1b ); a localgroup node 111 and a remote group node 112 (FIG. 1c ); and a local groupnode 111, a remote group node 112, and an individual node 120 (FIG. 1d). Of course, many other configurations involving a group node 110 andother group nodes 110 or individual nodes 120 are possible. As will bediscussed later, any of these configurations (as well as a configurationhaving a group node 110 only) may be used for a presentation using mediapresentation software 224 (e.g., a slideshow or a video) from a local PC201. Note that an individual node 120 is always considered a remote node140 for our purposes, while a group node 110 may be either an individualnode 120 or a remote node 140.

FIGS. 2a and 2b illustrate components of an individual node 120 and agroup node 110, respectively. The individual node 120 is a PC 200 thatincludes video chat software 210 (or video conferencing software), whichwould be executing during the chat session, and sending and receivingaudio and video streams through a connection to communication system211. A PC user interface 212 is used for configuring, initiating, andterminating execution of the video chat software 210. A PC microphone223 is used to capture audio by an individual node 120; a PC camera 221captures a video stream by an individual node 120. A PC monitor 222displays video received by an individual node 120 from other nodes; a PCspeaker 220 (or a headset) outputs sound received by an individual node120 from other nodes. Some of these components may be internal to the PC200, and others may be external, coupled wirelessly or by wire. Some PCs200 may not have all the components, and still be able to participate ina video chat session as an individual node 120. For example, a PC 200without a PC camera 221 might still participate, but other participantswould receive audio but not video from this participant. Some of thetypes of PCs 200 that might serve as an individual node 120 include alaptop computer 230, a smart phone 231, and a tablet computer 232.

The group node 110 configuration of FIG. 2b includes a PC 200. Thereneed be nothing special about this PC 200, although preferably it willbe a desktop or laptop computer. The group node 110 illustrated alsoincludes a speaker 260, a camera 261, a monitor 262, a microphone 263,and a user interface 264, which are elements of a PC-based videoconferencing system 250, external to the PC 200. The PC 200 may stillhave its own speakers, camera, monitor, and/or microphone, but those ofthe video conferencing system 250 will be better suited for group use ina conference room. The PC 200 of the group node 110 may include (intangible storage) and execute media presentation software 224 (e.g.,slideshow software; movie, TV, or other video software; or software suchas a browser that enables the PC to obtain video and audio streams froma network). When the video conferencing system 250 is used inpresentation mode, this information may be presented by the conferenceroom equipment of the video conferencing system 250.

FIG. 3 is a conceptual diagram illustrating an embodiment of a PC-basedvideo conferencing system 250. A group node 110 that includes a PC-basedvideo conferencing system 250, is engaged in a video chat session withtwo remote nodes 140; namely, a group node 110 and an individual node120. The system 250 is located in a room 380, which also containsseveral participants 350. The participants 350 share a single local PC201, which they use to run video chat software 210. The videoconferencing system 250 of FIG. 3 includes a dock 310, a room media unit(RMU) 320 connected by what we will refer to as a audio-visual (A/V)“pipe” 390, or simply a pipe 390. The pipe 390 may be a cable, or anyother type of communication system 160. The dock 310 includes one ormore interfaces for connections to the local PC 201 (“local” in thesense that it is in the room 380), whereby audio streams, video streams,and control information can be transferred between the two devices. Thedock 310 also a tactile user interface (UI) 311, which may include akeyboard 312 and other controls. These controls may be physical buttons,knobs, and so forth, they may be touch screen controls, or any other UIcontrols whereby a user can communicate with a smart device. The dock310 may have a dock display 314 that, for example, displays informationentered from the tactile UI 311, information received from the local PC201, or system status information. The dock 310 will preferably have aroom microphone 319, which may be part of a speakerphone 313. The mic319 will be used to capture audio from the room 380 (e.g., voices ofparticipants when speaking) for transmission to the remote nodes 140.The speakerphone 313 may or may not be configured for telephoniccommunication, such as through a wired or wireless phone system.

The RMU 320 may contain, or be coupled to, one or more speakers 321 andone or more cameras 322 or camera systems. Audio received by the localPC 201, via its video chat software 210, from the remote nodes 140 isoutput through the speakers 321. The speakers 321 may also be used, whenthe system is in presentation mode, to output audio from the room mic319 or from a mic in a PC 200, either local or remote. In conferencemode, video captured by the camera 322 will be transmitted to local PC201, and then from the local PC 201, again via the video chat software210, to the remote nodes 140.

The RMU 320 may contain, or be coupled to, one or more monitors 330. InFIG. 3, the monitor 330 is shown as external to the RMU 320, but in someembodiments, the monitor 330 and some or all other RMU 320 componentsmight be integrated into a single housing. In conferencing mode, themonitor 330 may output video from one or more remote nodes 140. Inpresentation mode, the monitor 330 may output video from a PC 200,either local or remote.

Preferably, the pipe 390 will be an inexpensive, standard off-the-shelf,component, such as a single CAT 5, CAT 6, or CAT 7 cable. In otherembodiments, other forms of wired or wireless transmission systems maybe used, alone or in combination.

Docking Station

FIG. 4 illustrates components of a docking station 310 of a PC-basedvideo conferencing system 250 in more detail. The dock 310 may include atactile UI 311. The tactile UI 311 might be used, for example, forcoordination with the local PC 201 in setting up and administeringexecution of the video conferencing system 250; entering telephonenumbers for communicating by phone with, or connecting with remote nodes140; setting up or manipulating the speaker 321, camera 322, monitor330, mic 319, or the speakerphone 313. In addition to possibly providingaccess to a telephone system, a microphone 319, possibly included in thespeakerphone 313, may be used to capture audio information from theroom, for transmission through the local PC 201 to the remote nodes 140.Preferably, the speakerphone 313 will produce HD audio, possibly byusing echo cancellation technology. The dock display 314 has alreadybeen described. The elements of the dock user interface (e.g., tactileUI 311, mic 319, dock display 314, speakerphone 313) are controlled andmanaged by a dock UI controller 410. The dock 310 has interfaces forexchanging information with the local PC 201. Arrows, typified by arrow421 show exemplary directionality of transmissions through theinterface.

During video conferencing/chat, the dock 310 receives remote audio andvideo streams from the remote nodes 140 through the local PC 201, andsends local audio and video streams to the remote nodes 140 through thelocal PC 201. Note that a television monitor can display video in HDMIformat, but not video in USB format. Consequently, it is preferable thatthe dock 310 receive remote node 140 video from the local PC 201 througha PC HDMI interface 422. Alternatively, the video input may be YCbCr,RGVHV, or any other format. The dock 310 may have multiple video (and/oraudio) ports, and the logic to automatically switch between them,depending on what is discovered to be connected. Audio from the local PC201 can be received through a PC USB A/V interface 420, and both audioand video from the dock 310 to the local PC 201, intended for the remoteindividual nodes 120, can also be transmitted through the PC USB A/Vinterface 420. The dock 310 may also include a PC USB control interface424, through which control commands from the local PC 201 to configurethe video conferencing system 250 can be received, and conversely.

The dock 310 communicates audio, video, and control information with theRMU 320. In principle, any communication system that can achieve thatwill do. Preferably, however, communication with the RMU 320 will bethrough a single cable, which we refer to as an A/V pipe 390, coupled tothe dock 310 through a dock A/V pipe interface 490. Preferably, thecable will be an inexpensive, off-the-shelf product, such as CAT 6cable.

A variety of information must pass from the dock 310 through the A/Vpipe 390 to the RMU 320, including, for example: video information inHDMI format from the remote nodes 140, via the local PC 201; audioinformation in USB format from the remote nodes 140, via the local PC201; control information from the local PC 201; and control informationfrom the tactile UI 311. In some embodiments, some or all of the controlinformation may be converted into a video representation, and configuredto overlay video output on the monitor 330. Additionally, videoinformation in USB format from the RMU camera 322 passes from the RMU320 through the A/V pipe 390 to the dock 310.

A dock media processor 400 is responsible for channeling and managingthe information flows through the various interfaces. This includeshandling data format, timing, and synchronization. The dock mediaprocessor 400 includes a dock video processor 401 for managing the videoinformation in both directions; a dock audio processor 402 for managingthe audio information in both directions; and a dock pipeassembler/scheduler 403 for handling the timing and synchronizationrequired to integrate all the information being passed through the A/Vpipe 390.

Some dock 310 embodiments may also include a communication bridge 430 tothe phone system interface 440. This arrangement may allow video chatsoftware 210 running on the local PC 201 to communicate with a telephonecommunication system, with the dock 310 serving as intermediary betweenthe local PC 201 and the telephone system.

Some dock 310 embodiments may also include a network interface 450 toprovide access to a communication system 160, such as the Internet or alocal area network. That access may be passed through to the local PC201 through a PC network access interface 425.

Room Media Unit

FIG. 5 is a schematic diagram illustrating a RMU 320, includingexemplary components and interfaces, of a PC-based video conferencingsystem 250. The RMU 320 may include, in a housing, one or more speakers321 that output sound received from the remote nodes 140 via the localPC 201 and dock 310. The RMU 320 may include one or more cameras 322,that capture video information from the conference room 380 or otherarea where the participants 350 in the group node 110 is gathered. Acamera 322 may be of any type, and have functionality that ranges fromstatic to highly complex. Preferably, if the camera 322 is static, thenit will have a field of view that is at least 70, or at least 80degrees. The camera 322 might have a variable field of view, such asapproximately 3 degrees to 80 degrees; in this case, the maximum fieldof view should be at least 70, or at least 80 degrees. A camera 322 mayimplement automatic tracking of speakers; it may have the capability tofocus on individual speakers, or the room 380 as a whole. The RMU 320may communicate through an interface, such as a monitor HDMI interface531 to one or more monitors 330 external to the RMU 320; in otherembodiments, a monitor 330 (shown dashed in the figure) may beconfigured as with a housing of the RMU 320 itself.

The RMU 320 may communicate a variety of information with the dock 310through the A/V pipe 390. Consequently, the RMU 320 may include a RMUmedia processor 500. Like the dock media processor 400, the RMU mediaprocessor 500 is responsible for receiving, scheduling and formattinginformation being communicated through a RMU A/V pipe interface 590 withthe dock 310, in both directions. As such, it may include a RMU videoprocessor 501, a RMU audio processor 502, and a RMU pipeassembler/scheduler 503.

Room Presentation of Audio/Video from Remote Node

FIG. 6 is an information flow diagram 600 illustrating the flow ofreal-time audio and video streams from a remote node 140 to a PC-basedvideo conferencing system 250. This diagram illustrates both a systemembodiment and a process embodiment of some of the concepts of theinvention. In the diagram, heavily-outlined boxes indicate sources ofinformation from within the video conferencing system 250 itself.Audio/visual information 601 is transmitted from the remote node 140,which is running video chat software 210 (or video conferencingsoftware), through communication system 160 to local PC 200. Settings inthe PC 200 allow it to specify that the its video will be output (inthis embodiment) via HDMI connection; and that audio will transmitted(in this embodiment) via USB connection. The dock media processor 400receives this information as 603 and 604, respectively.

Control information 605 from the tactile UI 311, and status information606 from the speakerphone 313 may be transmitted to the dock UIcontroller 410, which will in turn transmit control information controlinformation 608 to the dock media processor 400. Some controlinformation may be used to control the system; some control informationmay be converted by the dock video processor 401 into a video format,e.g., for overlay on the monitor 330 over the video stream originatingfrom the remote node 140.

Video 603 received from the local PC 201 is reformatted by the dockvideo processor 401 into a form suitable for transmission through theA/V pipe 390 to the RMU 320. As already mentioned, when controlinformation 608 is received from the dock UI controller 410, the dockvideo processor 401 may select some or all of that information tooverlay the local PC 201 video on the monitor 330; that data will bereformatted by the dock video processor 401 for A/V pipe 390transmission. Audio 604 received from the local PC 201 is reformatted bythe dock audio processor 402 into a form suitable for transmissionthrough the A/V pipe 390 to the RMU 320. The dock pipeassembler/scheduler 403 schedules and assembles video from the dockvideo processor 401 and audio from the dock audio processor 402 into anintegrated stream of packets, which contain information about timing, sothat the RMU media processor 500 is able to preserve synchronization ofthe audio and video output from the system.

The A/V pipe 390 carries media stream 622 from the dock media processor400 to the RMU media processor 500. Preferably, the A/V pipe 390 will bea CAT 5, CAT 6, or CAT 7 cable, but any other form of wired or wirelesscommunication system might be used instead.

Information received 630 from the A/V pipe 390 is disassembled by theRMU pipe assembler/scheduler 503 into its video component 640, which itsends to the RMU video processor 501, and its audio component 641, whichit sends to the RMU audio processor 502. The RMU video processor 501formats and sends video 650 to the monitor 330. This is preferably inHDMI form, but it could be RGB, NTSA, or VGA, or any other formatcapable of being displayed on a monitor. The RMU audio processor 502formats and sends audio 651 to the RMU speakers 321.

Room Audio/Video Capture and Transmission to Remote Node

FIG. 7 is an information flow diagram 700 illustrating the flow ofreal-time audio and video information to a remote node 140 from aPC-based video conferencing system 250. This diagram illustrates both asystem embodiment and a process embodiment of the invention. In thediagram, heavily-outlined boxes indicate sources of information fromwithin the video conferencing system 250 itself.

Video is captured from the conference room 380, or other group setting,by the camera 322 of the video conferencing system 250 and transmitted701 to the video processor 501 of the RMU media processor 500. The RMUvideo processor 501 converts the video into a format suitable fortransmission over the A/V pipe 390. The RMU pipe assembler/scheduler 503receives 702 the video from the RMU video processor 501, and forms datapackets having timing/synchronization information sufficient fordisassembly by the dock pipe assembler/scheduler 403 that preserves thereal-time nature of the audio and video streams. Packetized informationsent 703 by the RMU pipe assembler/scheduler 503 passes through the A/Vpipe 390, and is received 710 by the dock pipe assembler/scheduler 403.The dock pipe assembler/scheduler 403 disassembles information from theA/V pipe 390 and sends it 712 to the dock video processor 401. The dockvideo processor 401 reformats 713 the video into USB, and sends 730 itto the local PC 201.

Audio is captured 706 from the conference room 380, or other groupsetting, by the room microphone 319. This audio is received 722 by thedock audio processor 402, which reformats the audio and sends 731 it tothe local PC 201 in USB format. Some status or control data enteredthrough the tactile UI 311 of the dock 310 that is transmitted 605 bythe dock UI controller 410 to the dock video processor 401 may bereformatted and sent 730 as USB video to the local PC 201. Ultimately,A/V information 740 is transmitted to the remote nodes 140.

Media Presentation System

The same components and methods already described can also be applied toa local room 380 presentation. In other words, the system hasapplicability for both video conferencing/chat, and for localpresentation. In the local presentation mode, audio, video, and controlinformation from the local PC 201 is presented on the monitor 330 andthe speakers 321. The local PC 201 might be executing, mediapresentation software 224, such as slideshow or movie/TV software. Audioand video may be received by the dock 310 from the local PC 201 throughthe same interfaces shown in FIG. 4. Audio might, alternatively or inaddition, be captured from the room mic 319, and presented on thespeakers 321. Note that the monitor 330 might be replaced with aprojector/screen combination, for use in a larger room.

A presentation conducted on the local PC 201 can also be transmitted toremote nodes 140, using the same video chat software 210 alreadydiscussed. We will refer to this as presentation-over-chat mode. Forexample, a speaker might run slideshow software on the local PC 201,making a local room presentation. The voice of the speaker is capturedby microphone of the speakerphone 313. The slide presentation istransmitted to the dock 310, to which the local PC 201 is connected. Thedock 310 may route the video to the monitor 330, the audio to thespeakers 321, and both the audio and video to the local PC 201 fortransmission via video chat software 210 to remote nodes 140. Questionsof the speaker may also be received from the remote nodes 140. Thismight be facilitated by the bidirectional transceiver system of FIG.8-11.

In summary, the system 250 may be used in at least three modes: videochat mode (which might also be used to present a lecture or otherpresentation, originating from a remote node 140, in the conferenceroom); local presentation mode; and presentation-over-chat mode.

Bidirectional A/V: Opportunistic Sequencing and Transmission

Many types of systems might be used for communication between the dock310 and the RMU 320 of a PC-based video conferencing system 250, asshown in FIG. 3-7. We now describe a particular configuration of A/Vpipe 390 that has much more general applicability. Note that the A/Vpipe 390 described below has specific implementation details, but thepractitioner in the art will realize that many of these details can bemodified within the inventive concepts illustrated thereby.

This A/V pipe 390 facilitates bidirectional transmission of uncompressedvideo, audio, control, network, and power over a CAT 5, CAT 6, or CAT 7cable, or other cable having similar architecture and transmission rateat least equal to a minimum adequate transmission rate. The minimumadequate transmission rate can be estimated as the sum of the targetvideo rate, the audio rate (e.g., 2 Mbit/s), and the control/header rate(e.g., 1 Mbit/s). CAT 6 cable, which we will take as exemplary, canhandle 60 frames per second. Cables having slower transmission rates canbe accommodated by reducing resolution of the video, or by having lowervideo frame rate.

FIG. 8 is a conceptual diagram showing four types of bidirectionaltransmissions between a pair of media appliances 800, namely mediaappliance A 800 a and media appliance B 800 b. Each media appliance 800includes a bidirectional transceiver 810, namely bidirectionaltransceiver A 810 a and bidirectional transceiver B 810 b, respectively.The bidirectional transceivers 810 can simultaneously handle four mediatypes 820, in both directions; namely, an audio stream 830; a videostream 831; a UI control channel 832; and network connectivity 833. Theaudio and/or video can be transferred uncompressed. The audio stream 830might transfer audio from a microphone 871, or to a speaker 870. Thevideo stream 831 might transfer video from a camera 840, or to a monitor841. The UI control channel 832 might transfer control information to orfrom a tactile UI 850. A computer 860 may receive network connectivity833, e.g., Ethernet at 10/100/1000, and also exchange audio, video, andcontrol with the remote media appliance 800 in both directions. The A/Vpipe 390 may also transfer power from one of the media appliances 800 tothe other.

FIG. 9 depicts a pair of bidirectional transceivers 810 connected by anA/V pipe 390, which in this embodiment is a CAT 6 cable 811. (Note thatCAT 5 and CAT 7 cables have essentially the same structure as CAT 6cable 811.) Each bidirectional transceiver 810 includes a mediatransmitter 900, a media receiver 901, a network transmitter 910, and anetwork receiver 911. (We adopt the convention that, with extensions ‘a’or ‘b’ may designate a particular transceiver, as in 900 a, or aparticular differential wire pair, as in 902 a.) Each transmitter in onebidirectional transceiver 810 is connected to a counterpart receiver inthe other bidirectional transceiver 810 by a respective differentialwire pair 902 (i.e., 902 a-902 d) on the CAT 6 cable 811. The result isconnectivity to send and receive both media and network in bothdirections. The network transmitter 910 and network receiver 911 pairsalso carry 24 Vdc power on differential pair 3 902 c and differentialpair 4 902 d, allowing either enclosing media appliance 800 to bepowered by the other; in FIG. 9, a load 921 on media appliance B 800 bis powered by a power supply 920 on media appliance A 800 a.

The media transmitter 900 and media receiver 901 pairs utilize a uniqueapproach to communicate multiple media types 820, such as those shown inFIG. 8, in either direction within the CAT 6 cable 811. The pairimplement a transport layer, a protocol layer, and data layers. Thetransport layer has been illustrated, e.g., by FIG. 9. The protocol anddata layers are illustrated, e.g., by FIG. 10.

Media Transmitter

As shown in FIG. 10, the media transmitter 900 (e.g., 900 a) accepts avideo source 1001 a, audio sources 1002 a, and control sources 1003 afrom the associated media appliance 800. The media transmitter 900accepts video-in 1004 a with resolutions up to 1080 p and 60frames/second. Multiple standards-based digital video streams can beaccepted to include BT.656 and BT_A120. The media transmitter 900accepts one or more channels of digital synchronous audio stream 1005 a.The audio sources 1002 a can be Pulse Code Modulated (PCM) formats. Themedia transmitter 900 accepts input 1006 a from one or more controlsources 1003 a and supports multiple standards based inter-devicecommunications protocols to include UART, SPI, Parallel, I2C. Inputstreams to the media transmitter 900 are labeled with exemplaryprotocols.

Media Transmitter: Input Formatter

The input reformatter 1010 a includes logic, possibly including a videoformatter module, an audio formatter module, and a control reformattermodule. These logic modules are not shown explicitly in FIG. 10 to avoidtoo much congestion in an already crowded figure; but theirfunctionality will be described here, and individual output arrows areshown in the figure.

The input video formatter converts the format of the video-in 1004 a tooutput, for example, 8 bit YCbCr video 1011 a at, for example, 720 presolution and 60 frames per second. The video formatter may apply videoscalar, color space conversion as appropriate to maintain the 8 bitYCbCr video 1011 a at 720 p resolution.

The input audio formatter accepts 1005 a N audio channels via I2Sformat, multiplexes the N audio channels, and aggregates them into asingle time division multiplexed audio stream 1012 a. The input audioformatter also applies decimation or interpolation to audio samples tocomply with the 16 bit sample resolution used in transport. Sample rateconversion may also be applied (as needed) to convert an input audiosource 1005 a to a 48 KHZ sample rate.

The input control formatter accepts 1006 a N control channels ofstandards based inter-bus communication protocols. This includes The Ncontrol channels are aggregated into a single control stream 1013 a.

Media Transmitter: Packetizer

The packetizer 1020 a prepares the data payloads (video, audio, control)for transmission to the media receiver 901. A respective module of thepacketizer 1020 a for each of the video, audio, and control streamsapplies a digital header word to the digital data of the media stream.The header includes metadata, such as the origin of the stream sourceand the destination for the stream at the far-end media appliance 800.The header may also include other metadata, such as a description ofmedia type (video, audio, control), format, and size. The header mayalso include handshaking and data validity information used by the mediareceiver 901 of the far-end media appliance 800 for reconstruction anderror correction of payload packets.

Media Transmitter: Input Adaptive Rate Multiplexer

The input adaptive rate multiplexer 1030 a prioritizes the inputstreams, with (preferably, but not necessarily) the packetized audiostream 1031 a having the highest priority in communication between mediaappliance A 800 a and media appliance B 800 b. Video payload bandwidthvaries (increases or decreases) based upon the image content being sentover the communications link. The logic determines/detect periods oflower audio bandwidth and injects a lower priority packet, e.g., acontrol or a video packet into the assembled media stream. We call this“opportunistic sequencing”. The non-video packets are called side-bandchannels.

The audio side-band channel contains audio data packets to be sent tothe media RX2 901 b. The control side-band channel contains control datapackets, also to be sent to media RX2 901 b. The protocol controlchannel 1015 a consists of communications used by the protocol logic toregulate bit rate transmit speeds based upon available receiver buffermemory in bidirectional transceiver B 810 b. The side-band channelprovides a method to prevent overflow or error conditions between themedia transmitter 900 and media receiver 901 pair.

The input adaptive rate multiplexer 1030 a also includes priorityscheduler 1035 a. This component uses software and switch 1034 a foropportunistic sequencing, prioritizing which packet types are sentwithin the media stream during low bandwidth conditions; for example,the priority might be (1) audio; (2) control; (3) protocol; and (4)video. Based upon the priority level of a side-band channel packet type,side channel router 1036 a may inject the packet payload into theside-channel stream, which is then combined with the video stream 1037 aby MUX 1038 a to form the media stream to be sent to the media receiver901 (e.g., media RX2 901 b).

The adaptive rate controller 1039 a and adaptive rate controller 1039 bmay regulate the transmission speed of the video stream (and embeddedside-channels) to prevent overflow conditions; monitor or correct errorconditions; or trigger retries of transmissions. Information is sharedbetween adaptive rate controller 1039 a of media TX1 900 a and theadaptive rate controller 1039 b of media RX2 901 b using protocolside-band channel 1060. The adaptive rate controller 1039 a may controland communicate with protocol control channel 1015 a, as indicated byarrow 1016 a. The adaptive rate controller 1039 b may control andcommunicate with protocol control channel 1015 b, as indicated by arrow1016 b.

Media Transmitter: Transport Layer

The transport layer 1040 a refers to the electrical and physical cableinterface 1050 a between media TX1 900 a and media RX2 901 b. Thetransport layer may use a SerDes 10 b/8 b encoding scheme(http://en.wikipedia.org/wiki/SerDes) over a differential cable pair(e.g., differential pair 1 902 a) on the CAT 6 cable 811 fortransmission of media stream packets. The maximum data rate may be 1.562Gbit/s. However, the system might use a higher or a lower maximum datarate, depending upon capabilities of the specific hardware componentsused, or upon needs.

Media Receiver

As shown in FIG. 10, the media receiver 901 (e.g., media RX2 901 b)receives the media stream from the corresponding media transmitter 900(e.g., media TX1 900 a) and converts it back into separate streams:video stream video-out 1004 b to video destination 1001 b; audio streamsaudio-out 1005 b to audio destinations 1002 b; and control streamscontrol-out 1006 b to control destinations 1003 b. Many of thecomponents and streams of the media receiver 901 have clear counterpartsin media transmitter 900; for the sake of brevity, such components ofmedia receiver 901 are labeled with reference numbers, but will notnecessarily be described explicitly again in the text.

Media Receiver: Transport Layer

The transport layer 1040 b decodes the SerDes 10 b/8 b media stream fromthe physical layer (i.e., CAT 6 cable 811 and cable interface 1050 b)and sends the decoded stream to output adaptive rate demultiplexer 1030b.

Media Receiver: Adaptive Rate Demultiplexer

The packet parser 1038 b detects side-band channel headers within thevideo stream. When one is detected, packet parser 1038 b extracts thepacket from the video stream and sends it to side channel router 1036 bfor delivery. The side channel router 103613 determines a destinationaddress for the data and routes 1034 b the data to the depacketizer 1020b. The depacketizer 1020 b strips sideband headers from audio stream1031 b, control stream 1032 a, and protocol channel 1033 b to preparefor native media formats.

Digital video is a synchronous data source requiring precision clockingbetween source and destination transducers. The video reclocker 1021establishes synchronous video clocks to be used with the video data.Video is regenerated by the receiving transceiver, which is the sourceof the video clock.

The audio interpolation reclocker 1022 establishes a synchronous audioclock by recreating a given (e.g., 48 KHZ) frame clock from the audiodata samples. Receiver media RX2 901 b is provided the audio frame ratefrom protocol control channel 1015 a of media TX1 900 a via protocolcontrol channel 1015 b. Receiver media RX2 901 b creates the sequence ofaudio frames based upon this rate. Audio sample data is clocked intothis recreated audio frame. The reclocker automatically realigns sampledata by shifting bit right or left until the frame sync and audio dataare in alignment, interpolating frames as necessary.

FIG. 11 illustrates interpolation by an audio interpolation reclocker1022. The depacketizer 1020 b sends audio frame sequence 1100 to theinterpolation reclocker 1022. Each audio frame spans an interval oftime. Frames such as Frame-1 1111 and Frame-2 1112 are held in delaybuffer 1120 until needed. The delay buffer 1120 may hold two or moreframes. When a master audio clock 1130 determines that an interpolatedaudio frame 1150 that represents a particular time X 1132 should beoutput, it sends a trigger 1131 to identify the audio frames that needto be clocked into the output stream. A weighted interpolator 1140performs a weighted average of some or all frames from the buffer, theweighting taking into account where time X 1132 is located relative tothe start and end times of the frames.

Media Receiver: Output Reformatter

The output reformatter 1010 b in FIG. 10 includes video, audio, andcontrol logic modules. The video reformatter module accepts the 720 p/60YCbCr video format used in communications system and modifies videostream 1011 b to the desired consumption format to be used by videodestination 1001 b. The audio reformatter module deconstructs the TDMstream in the communications system and creates an I2S or otherappropriate format to be used by an audio destination 1002 b. Thecontrol reformatter module formats the control data in thecommunications system to the desired standard based inter-bus protocols(e.g., I2C, SPI, UART). Output streams from the media transmitter 900are labeled with exemplary protocols. Digital media and control streamsare consumed by video destination 1001 b, audio destinations 1002 b, andcontrol destinations 1003 b of media appliance B 800 b.

Power Over A/V Pipe

As illustrated by FIG. 9, CAT 6 cable 811 and similar communicationsystems support a method for carrying power originating from mediaappliance A 800 a to media appliance B 800 b. This method eliminatesneed for external power supplies for the secondary appliance. Thesesystems also include an automated detection and protection scheme toprevent equipment damage associated with accidental connection tonon-supported devices. Power at 24 Vdc is supplied to differential pair3 902 c and differential pair 4 902 d, and to the load 921 on the CAT 6cable 811.

The detection and protection scheme may be described as follows.Switched DC levels which are compared to determine if media appliance A800 a (Source) is connected to a compatible load 921. Load detection andqualification is performed on differential pair 2 902 b of CAT 6 cable811. Disconnect detection is performed on differential pair 1 902 a.Power is applied on differential pair 3 902 c and differential pair 4902 d.

Prior to applying power 920 to differential pair 3 902 c anddifferential pair 4 902 d, a +5V probe voltage is switched onto one-halfof differential pair 2 902 b on the Source side. The other half of thedifferential pair 2 902 b has a DC voltage comparator circuit connectedon the Source side. The comparator determines whether an Ethernet deviceis connected to the Source. The probe voltage is current limited so,should an Ethernet device be connected, no damage will result to theEthernet device. If an Ethernet device is connected, the Ethernettransformer will create a short between the two wires of differentialpair 2 902 b and create a specified voltage of known level for thecomparator to detect. If an Ethernet device is present, system powerwill not be applied to diff pairs differential pair 3 902 c anddifferential pair 4 902 d. If an Ethernet device was not detected, the+5V probe voltage is switched off and a higher +24V, current limitedprobe voltage is applied, again on differential pair 2 902 b. Should anappropriate load be connected, this higher probe voltage will causeisolated back-to-back zener diodes located between the two differentiallines of the load device to break down into conduction and create aknown level which is detected by the sources comparator. System powercan then be safely applied to differential pair 3 902 c and differentialpair 4 902 d. Disconnect function operates on differential pair 1 902 a.This is simply performed by equally energizing the differential lines onthe load side with a logic level bias voltage of +3.3V and detectingwith logic on the Source. Break the link connection and the load powergoes away as well as the bias voltage on the differential pair 1 902 alines. Load power 920 would then be switched off at the Source andre-qualification of the link would take place as detailed above.

CONCLUSION

Of course, many variations of the above illustrative examples arepossible within the scope of the invention. The present invention is,therefore, not limited to all the above details, as modifications andvariations may be made without departing from the intent or scope of theinvention. Consequently, the invention should be limited only by thefollowing claims and equivalent constructions.

What is claimed is:
 1. A method, comprising: a) receiving a first mediastream from a bidirectional media communication interface in a remotedocking station, through a single twisted pair cable, which is connectedto a tangible communication port of a bidirectional media communicationinterface within a room media unit (RMU); b) disassembling andreformatting frames from the first media stream into a first videostream and a first audio stream, c) transmitting data from the firstvideo stream to a monitor in the RMU, or through a monitor interface inthe RMU, d) transmitting data from the first audio stream to a speakerin the RMU, or through a speaker interface in the RMU, e) receiving asecond video stream from a video camera in the RMU, or through a videocamera interface in the RMU, f) reformatting and assembling, with theRMU, frames from the second video stream into a second media stream, andg) transmitting the second media stream from the RMU through the portover the single twisted pair cable to the remote docking station.
 2. Themethod of claim 1, further comprising: h) receiving electrical power bythe RMU, wherein the RMU receives electrical power solely through theport when the RMU is powered up and in normal operation.
 3. The methodof claim 1, wherein the second media stream is transmitted in anuncompressed format.
 4. The method of claim 1, wherein the port includesa CAT 5, CAT 6, or CAT 7 cable connector.
 5. The method of claim 1,wherein the camera has a variable field of view.
 6. The method of claim1, wherein the camera has a static field of view of at least 70 degrees,or a variable field of view having a maximum value of at least 70degrees.
 7. The method of claim 1, wherein the RMU media communicationinterface includes a RMU bidirectional transceiver, communicativelycoupled to the port, and wherein the RMU bidirectional transceivercontains a media transmitter, a media receiver, a network transmitter,and a network receiver.
 8. The method of claim 1, wherein the step oftransmitting data from the first audio stream uses an interface in theRMU, distinct from the bidirectional media communication interface ofthe RMU, to a speaker external from the RMU.
 9. The method of claim 1,wherein the step of transmitting data from the first video stream usesan interface in the RMU, distinct from the biodirectional mediacommunication interface of the RMU, to a monitor external from the RMU.